1) Field of the Invention
This invention relates generally to fabrication of semiconductor devices and more particularly to an etch process for fabricating a vertical hard mask/conductive pattern profile.
2) Description of the Prior Art
In semiconductor fabrication, metal structures are commonly formed by patterning one or more blanket conductive layers. These blanket conductive layers typically have a blanket hard mask layer formed thereover. The hard mask layer protects the underlying conductive layer from damage during etching of higher layers as well as preventing diffusion into and out of the underlying conductive layer. One material that is often used to form a hard mask layer over a polysilicon conductive layer is silicon oxynitride. However, patterning a polysilicon layer and silicon oxynitride hard mask layer using prior art processes can result in a T-shaped hard mask conductive layer profile, reducing the width of the conductive structure thus formed. It is desireable to provide a method of patterning a hard mask and underlying conductive layer which can maintain a more vertical profile.
The importance of overcoming the various deficiencies noted above is evidenced by the extensive technological development directed to the subject, as documented by the relevant patent and technical literature. The closest and apparently more relevant technical developments in the patent literature can be gleaned by considering the following Patents.
U.S. Pat. No. 5,139,968 (Hayase et al.) teaches a method for forming a T-shaped gate electrode.
U.S. Pat. No. 5,407,870 (Okada et al.) discloses a process for forming a SiON layer.
U.S. Pat. No. 5,766,993 (Tseng) discloses a process for forming a poly gate and contact.
U.S. Pat. No. 5,700,739 (Chiang et al.) discloses an oxynitride hard mask and etch process using a reactive ion etch with a fluorine containing ethant.
U.S. Pat. No. 5,731,239 (Wong et al.) shows a silicon oxynitride hard mask and a salicide process.
U.S. Pat. No. 5,766,974 (Sardella) shows an oxynitride layer on an intervener dielectric to provide an etch stop for a Cl.sub.2 overetch.